The present invention relates to a method for the feeding of contents comprising liquid as well as solid particles in the manufacture of packing containers by repeated transverse flattening and sealing of tubular packing material.
The invention also relates to an arrangement for the realisation of the method, this arrangement comprising devices for the transverse flattening and sealing of a packing material tube extending substantially vertically and filled with contents as well as elements extending into the tube for the feeding of contents as well as packing material tube.
Packing containers for e.g. milk or other liquid foodstuffs are manufactured generally from laminated, flexible material which comprises layers of paper and thermoplastics. A known packing container is formed in that a laminate web, during its advance through the packing machine, is successively converted to tubular shape by the joining together of its two longitudinal edges and sealing them to each other in a liquid-tight manner. The tube so formed is moved substantially vertically downwards through the machine at the same time as the contents are fed continuously via a feeding pipe introduced at the upper, open end of the tube which extends downwards inside the tube. At the lower end of the tube the machine is provided with reciprocating processing jaws co-operating with one another which comprises the passing material tube at equal distances so that transverse flattened zones are produced wherein the walls of the material tube are sealed to one another in a liquid-tight manner. The transverse sealing of the material tube takes place below the contents level and the tube is thus converted to coherent, substantially cushion-shaped packing containers completely filled with contents. After the cushion-shaped packing containers have been separated from one another by cutting through the transverse sealing zones a final shaping process is carried out so that the packing containers obtain the desired, e.g. parallelepipedic, shape.
The packing containers which are manufactured in the manner described above were usable up to now only for those liquid contents which wholly lack, or in any case contain only very small, solid particles, e.g. finely distributed fruit pulp in juice or the like. The reason for this is that any solid particles possibly present in the contents may on flattening of the material tube below the liquid level end up between the material layers which are to be sealed to each other and among other things cause leakages in the transverse seals at the top and bottom of the packing container. If contents in "solid" form (the designation "solid" is used in the description and the claims to designate contents in the form of individual, solid particles, e.g. larger bits of fruit, beans, pieces of asparagus or the like with or without a liquid part) are to be packaged, the feeding of the contents has to take place intermittently and in rhythm with the repeated transverse sealings of the tube so as to prevent the solid particles from disturbing the sealing operation. In other words, the feeding of a portion of contents of the desired volume to each packing container should be started as soon as the first (lower) transverse join of the packing container has been formed and be completed before the flattening and sealing of the second (upper) transverse join of the container of the package. In this manner it can be avoided that the solid particles of the contents get between the material surfaces sealed together in the transverse joins. The method is comparatively slow, however, since a high feed rate may cause the contents to spatter or be thrown about during the filling so that in spite of the feeding of the contents in portions the transverse join cannot be kept free from solid particles. The method also implies that the packing containers are not completely filled, since the risk of inclusions of solid contents in the transverse joins would then be considerably increased.
It is an object of the present invention to provide a method which makes it possible in the continuous manufacture of packing containers from tubular packing material to fill solid particles (bits of fruit etc.) together with liquid contents as well as individually, without the disadvantages experienced hitherto.
It is a further object of the present invention to provide a method of the aforementioned type which while retaining the high machine speeds existing up to now makes it possible to fill solid contents without increasing the risk of leaking packing containers.
These and other objects have been achieved in accordance with the invention in that a method of the type described in the introduction has been given the characteristic that the solid particles are fed to the tube in the form of a metered quantity as soon as a transverse flattening has been completed whereas the liquid is fed during a longer period which is ended only when the feeding of solid particles has been ended.
It is a further object of the present invention to provide an arrangement for the realisation of the abovementioned method, this arrangement being simple and reliable in operation and designed so that it can be used without major difficulties on known types of packing machines.
It is a further object of the present invention to provide an arrangement which is not subject to the disadvantages of similar arrangements known previously and which is uncomplicated and capable of being washed and sterilised in a simple manner.
It is a further object of the present invention to provide an arrangement which makes it possible to manufacture wholly filled as well as partly filled packing containers.
These and other objects have been achieved in accordance with the invention in that an arrangement of the type described in the introduction has been given the characteristic that the feeding elements comprise a flat pipe for the feeding of liquid and a second pipe for the feeding of solid particles, the second pipe being provided with a valve arrangement.
The method and the arrangement in accordance with the invention present many advantages in that they eliminate the disadvantages of previous constructions and methods and make it possible to make use of known principles of package formation for the manufacture of packing containers which are wholly or partly filled with contents comprising a larger or smaller, accurately metered portion of solid particles. The volume of contents in each individual packing container can be regulated with great accuracy, and fluids with solid particles of diverse kind can be filled. The method and the design of the arrangement eliminate the risk of particles of contents attaching themselves between the material surfaces pressed to each other in transverse joins and thus ensure completely tight transverse seals which make it possible to fill in aseptic as well as non-aseptic manufacture any types of contents which occur in practice in the foodstuffs branch.